Lenses, prisms, optical flats, and color filters (hereinafter collectively referred to as ‘optics’) are commonly used in laboratories and in equipment such as cameras, telescopes, magnifying glasses, and binoculars. The performance of an optic depends on three major characteristics: transparency in the spectrum of interest, shape, and refractive index.
In order for a material to be suitable for constructing an optic, it must absorb very little of the wavelengths it is intended to transmit—for example, a magnifying glass intended to be used by the naked eye should absorb very little of the visible spectrum. Suitable materials must also be able to hold a shape related to the intended function of the optic—for example, a plano-convex lens includes one flat and one convex surface, so a material may be suitable for constructing a plano-convex lens if the material can be formed into a shape with one flat and one convex surface. The refractive index of an optic determines how the path of a beam of light will be altered by the optic; a prism spreads white light into a rainbow due to each wavelength of the rainbow experiencing a different refractive index.
The quantitative traits of an optic, such as focal length and acceptance angle, are determined by a combination of the shape and the refractive index of the optic; a lower refractive index material uses a smaller radius of curvature to achieve the same focal length in a lens, and a higher refractive index material will result in a prism with a larger acceptance angle. Design constraints such as size or feasibility of construction may restrict what materials are valid for construction of an optic due to placing constraints on the refractive index.
Optics are usually constructed partially or entirely from a glass or plastic, or, less commonly, from a transparent liquid. These materials satisfy the three major characteristics listed above, and methods of constructing optics from these materials are widely known.
Although optics are present in many widely-used consumer products and technical equipment, the details of their construction and function are minimal or absent in most science curricula. This can, in part, be attributed to the fragility and cost of conventional optics; shattered glass poses a danger to students, and most optics are too expensive to be replaced frequently in classrooms. In addition, because glass and plastic require special training and equipment in order to form optics, children often do not participate in the construction process.
Cost and difficulty of manufacture can also cause projects requiring custom-built optics to be prohibitively expensive, especially when the project requires many optic components or when iterations of the project result in the destruction or obsolescence of one or more optics.
Some alternatives to glass and plastic exist that partially address the above problems for construction of optics. For example, gelatin lenses have recently gained popularity as an educational tool. However, gelatin deforms easily under its own weight, and so is not suitable for the construction of many types of optics. Gelatin is also delicate and very sensitive to motion, which further restricts its use to certain orientations. Gelatin is therefore not a valid material for the majority of optical equipment, interactive educational experiences, or scientific projects, which all usually utilize a wide range of shapes and orientations, tolerance for motion, and durability.
Some current methods of lens construction result in a lens that must be polished after the initial casting. In order for these methods to result in a lens suitable for optical applications, special equipment is required, increasing the time and cost of lens fabrication. Some current methods also destroy the mold used for casting the lens, limiting the consistency of lenses formed using these methods.